1. Field of the Invention
The disclosure refers to a screw vacuum pump, preferably for the compression of a medium, typically gas, with respect to atmosphere.
2. Discussion of the Background Art
Screw vacuum pumps have a suction chamber in a pump housing. Two screw rotors are arranged in the suction chamber. On their outer side, the screw rotors each have a helical thread, with the two threads of the screw rotors meshing in order to convey and compress the medium. Within the suction chamber, the medium conveyed is compressed from the suction side, i.e. the pump inlet, towards the pressure side, i.e. the pump outlet. Typical compression ratios of screw vacuum pumps are in the range from 1 to 106. Depending on the pressure present at the pump inlet, an over-compression can be caused in the screw vacuum pump. Such an over-compression, i.e., in the case of a pumping against atmosphere, a pressure above atmospheric pressure, results in a strong increase in the energy consumption of the screw vacuum pump. This leads to power losses, since an unnecessary compression, i.e. an over-compression, of the medium to be transported is performed.
In the interest of avoiding over-compression in screw vacuum pumps, it is known from DE 100 45 768, for instance, to provide an overpressure outlet. The overpressure outlet has a overpressure opening in a side wall of the suction chamber. An overpressure valve is arranged in the overpressure outlet.
It is an object of the present disclosure to design the overpressure outlet such that the risk of an overpressure occurring in the screw vacuum pump is reduced and the pumping performance as well as the energy efficiency of the screw vacuum pump is improved.